In general, when starting an internal combustion engine, if the internal temperature of the internal combustion engine, particularly, the cylinder wall temperature or the combustion chamber temperature, is low, friction loss occurs during movement of the piston and exhaust gas compositions deteriorates.
Therefore, in the prior art, a latent heat type heat storage material is accommodated in an internal combustion engine. There has been a proposal for a warm-up apparatus that stores heat generated by the operation of the internal combustion engine in the heat storage material and releases the heat stored in the heat storage material when the internal combustion engine is next started to accelerate warming of the internal combustion engine (refer to, for example, patent document 1).
A warm-up apparatus in the prior art includes a nucleation device having a pair of electrodes inserted into a heat storage material. Voltage is externally applied to the electrodes to activate the nucleation device. This nucleates the heat storage material, which is in a supercooled state, so as to accelerate phase transition and release heat from the heat storage material.
However, in the warm-up apparatus of the prior art, voltage is externally applied to the electrodes to accelerate the phase transition of the heat storage material. This requires insertion holes for inserting the electrodes into the heat storage material from the outer side and an electrical circuit for applying voltage to the electrodes. Therefore, an operation for forming holes extending through the heat storage material and seals arranged around the holes become necessary. Furthermore, an electrical circuit is also required. This inevitably increases the cost of the warm-up apparatus.
Patent Document 1: Japanese Laid-Open Patent Publication No. 11-182393